Universal telephone repeater



june 30, W, E. HARDING 2,046,119

UNIVERSAL TELEPHONE REPEATER Filed Sept. 16, 1933 2 Sheets-Sheet l X f L I S l,L Q

@Y gg; L 4% 3 m N $2, l; N

` gwwntoc WILLIAM E. HARDING 4Fume 30, l19315.

W. E. HARDING 2,046,119

UNIVERSAL TELEPHNE REPEATER Filed Sep'l). 16, 1935' 2 Sheets-Sheet 2 I QQQQQQDQ gmc/nto@ WILLIAM E. HARDING Patented June 30, 1936 UNITED STATES PATENT OFFICE 25 Claims.

The invention relates to telephone repeaters, and more especially to repeaters required in attenuated or long circuits in which it is necessary to amplify the voice currents carried by such circuits at intermediate points; and consists substantially in the construction and arrangement of parts disclosed in the accompanying drawings and pointed out more particularly in the claims.

It is a general object of the invention to provide an amplifying telephone repeater in which the usual or conventional artificial line is not required.

It is a primary object to provide a telephone repeater, which when considered from either end of same comprises a parallel-input E. M. F.- neutralizing circuit; an independent load-balancing circuit; a parallel-line output load-dividing circuit; an unbalance compensating circuit, and a Vernier balancing circuit.

The above and other objects are attained by the structure illustrated in the accompanying drawings, of which:

Figure l is a diagram of the invention as a whole; and

Figure 2 is an enlarged and modified portion of Fig. 1.

Similar characters of reference designate similar parts throughout the dil-ferent views.

Input and output balance This repeater is universal to all telephone circuits, and dispenses with the usual artificial line,

amplifying the power from the incoming line IA to the outgoing line I, turning to line I, not only the usual power which would go to the line I in present repeaters, but the power ordinarily lost in an articial line, in addition. This is accomplished by means of the parallel-line output loaddividing circuit 2; the load presented to output currents being equally divided across the zero points 3, as will be understood, of the independent load-balancing circuit 4, comprised in part by two transformers 5, one on each side, 6 1, of sf'd points of zero output potential, and co'nsisting of windings 8, 9, IIJ, II and I2, I3, I4, I5 respectively; the line windings I4 and I0 of which are in the aforesaid circuit 2, connected in series with the line I. Parallel to impedance I6 and winding i4 are two other windings II and I5, ene in each of the two said transformers 5, which are also in'series with the line I and winding I0, but which are made to neutralize each other with respect to output currents, as will be understood. Thus the series-parallel circuit 2 is so connected to evenly divide the output load between transformers 5; the output currents generated in windings and respectively in said transformers, being in the saine direction and adding; the E. M. F. of such currents being equalized by the manually adjusted line dividing-impedance I6;

the output E. M. F. of windings II and I5 mutually opposing and neutralizing.

The windings II, I4 and I5 are seriesparallel connected to the line I, by which arrangement the output E. M. F. of winding II 5 exactly opposes the output E. M. F. of winding I5; windings I! and i5 being differentially connected together and having series relation in the line I.

The input currents from the line I traverse the l0 parallel circuits 2 in such manner as to neutralize windings I4 and I5, traversing primary windings I4 and I5 in opposing inductive directions in that transformer in one half 2| of the load-balancing circuit 4, traversing primary windings i5 and il l5 in series, thus generating input E. M. F. in winding 9 in one half 25 of the independent loadbalancing circuit 4 including the input transformer 22, thence to the first audio tube 23, thence through the repeater as a whole to the 2O other associated line lA which is balanced in exactly the same manner as above described. Thus far it should be clear that the repeater is balanced with regard to output currents and that only one side of the independent load-balancing 25 circuit 4 is excited by input currents from the line I. Reiiective counter-E. M. F. from the line I is minimized by means of a third and compensating circuit 24, comprised of windings and I2, in each of the aforesaid transformers and in 30 series with variable impedance 25.

These two windings 8 and I2 are differentially connected and therefore neutralize each other with reference to output currents to the line I, thus causing no loss of output E. M. F. But one 35 of these windings 8, being in the transformer in which the input currents add in windings 50 and II, as above described, generates input currents from the line I (including reflective counter E. M. F.) through the other winding I2 in the 40 other transformer in which input currents from the line I are made to neutralize in windings I4 and I5; thus generating input currents inwinding I3 in the other half 2l of the independent load-balancing circuit 4. 45

In practice therefore, the variable impedance 25 is used, compromising output balance, output reaction and input volume within the scope of practicability.

A repeating coil 26 may be used across points 50 21 and 28 of circuit 24 with adjustable resistances at 25 and 29 as shown in Fig. 2, not altering the uses of circuit 2li.

The output power balance in the two transformers 5, comprised in part of windings IU and II, and I4 and I5 respectively, has been described to indicate the even division of the line load between the two transformers 5, in windings l0 and I4 respectively; the power of Winding I4 adding to that of winding lo.

vIt will be obvious that V the power generated in the two line windings I4 andI Il from the out-r putY primary windingsY 3 IJ 'and 3| ,of Vthe separate power transformerV comprised of windings 30, 3l, 32 and 33, and owing through windings 8 and I3'of Ythe'two balancing transformers 5 in series, having traversed secondary windings I4 and IIJ in an upward direction on the drawings goes to the line on one side 34 and back on the other side of the line to point I1; and Vthat toevenly divide the line load in windings I4 and I0 there' fore, the adjustable dividing'resistance I6 must be adjustedto the value of the impedance of the line VI thus neutralizing windings II and I5. toj l Voutput current, and windings i4 and. I5 to input currents through parallel circuit 2 Vresistance I6 being increased or decreased according as the line resistance increases orY decreases, to maintainV the absolute balance of circuit 2. Y

' Tite imbalance-compensating circuit But repeater unbalances dueA to line changes, are prevented in Ythis repeater because of the presence of the compensating Vcircuit 24, in which there is no current ownor output power dis- Y. sipation when the circuit 2 is balancedy but in which there is current iiow dueY to line changes, increasing orv decreasing line loadror impedance;

for'when the line resistance increases', for exam-V ple, there is less load in winding IU than in winding I4, thus increasing the impedance of primary windingl over that of primary winding I3; windings I4, and I5 having the greater load, Since dividing impedance I6f does not change except manually. `VThe increaseo'f line impedance inV winding I0 is elective inrwindings 8V and I2 of the compensating circuit; the greater loadin one transformer'over that of the other causing increased E. M. F. inV winding 8 and consequent current flowV from winding 8 through winding I2 and thus shiftingthe 1imbalance fromrthe line to the compensating circuit'V and preventing Vthe Vunbalance ordinarily due to such line changes;

g the current flow from. winding 8r throughr winding I2 Vbalancing the E. M. of Ywinding VI3 againstthat of winding 9; Vthe reverse action oc'-V Y"curring in case of decreased lineV impedance.

Y Y Vernier` balance d VI'hat part of theindependent load-balancing circuit 4 composed ,of the variable resistance or potentiometer 31 and vwinding 38 of the input'. k'transformer 22'is used as a Variable -or-vernier adjustment Vto balance outgoing or output Yvoltage in the primary circuit Srand 38 to obtahi absoluteV zeropotential of output currents at` points 3 and 3f; or to correct slight imbalances i over the zero points 3 and 3 or the input circuit,k

' in the windings comprising the circuit 4, including the center-tappedinductance 4D shown with bridged condense'r`4i; condensers 4I and 42 being used to by-pass slight unbalanced Youtput. Voltage Y YWinding 38 ofthen input transformer 22Y receives current from the potentiometer 31 in an oppositeY or opposing Y. direction tc that in winding 39 of the input transformer. Y

k Amplifier- Gain control Y Windings 35, 3|32 and 33 are all in one transformer, the source ofY outgoing or output power; the circuit being actuated "by amplifying tube 43 and its associated Vpreceding equipment.` Wind- 4ings 30 and -I, and Sand I3 areV primary with reference to output currents; windings I 0, II, I4 and arerprimary with reference to input cur- Vthus making the Vrepeater to line changes.

cuit with windings I5 and II, thus minimizing the neutralization ofl windings I4 andl "I5 with.V Vreference,torinput currents, and therefore relet us say, three volts.

Vtwo Voltslgcing via I4 to point I8, and onevolt YVia and II to point I8.; the one `Voltigoing via rents; windingsl 3.12. s, secondary in both cases. f

The volume output of either Vhalf of the repeater is controlled bydecibel-calibrated gain-V I .Y

potentiometers 44 and 44A. l

The plate circuit composed of windings 3l) and :Y Y 3| isfree'of shunting condensers and impedances,

' thus causing no lossV to input currents from line I through windings I0, II,V I4 and I5, and 32, 9,` I3 Y and33.Y Y* ,Y Y Y A variableinipedance may be used at point 45 balance more immune Y however reduces input amplitude'due the presence of resistance 45 in the parallel Parallel Voutput loud-duiding. circuit f trated by referring tc windings I0, II, I4-and I5Y Vin which the output power is equally dividedrf the potential generated in-each winding being,

It is seen thatV the E. generated inwind- Y ing I0 traverses the line I frornpoint 34to Ypoint I1 of the parallel circuit 2, where it woulddivide;

I5 and II from point I1 being in the opposite direction to theE. M. VF. being'generaied inwind- Y Ying and adding to thatgeneratedin winding il.

.'Ifiie E. -M. F. of three volts generated` in wind--` via iil'and liney `I from point'ISgto point 'I 1, and Y,

one volt goingvia IIand I5` ofthel parallel cir- V Vand I5 being in jrtheV` opposite directiorutoy the E. M. F. being generated'in winding II andadd- Y cuit KV2vk topoint', I1; the onevoltgoing via ii ingV to that generated inv winding I5; thusrneu-KV tralizingthe onevolt from'iIl'throu/gh I5 and II yfrom point I1to point-I8. Actually, the E. F. of iii' and I4does not so divide, since vthelil. M c-f I0 islof the same polarity and potential at point I1 as that of'V i4 at point I8; the F. Yof II being of the same potential and polarityYV at. point I8 as ,that of i5 at point I-1,`thus neutralizingwindings II and I5; f.

the impedance of I?.- and that ofthe line I being equal.

Windings I5Y and II are alsojdirectly inr` the',Y

circuit of Yline I betweenrpoints- I8 and I1, but 65,

exactly neutralize eachzother in said line, Vwith Vreference to outputrE. M. F.,windings I5 and II V being differentially*connected. Y

Independent load-balancing circuit Thus itis (clear, thatthe repeateris balanced; the E; M. F. of I5 being` exactly Ybalanced by thev E. M. F.'of Il, both inV the parallel circuit andl in the line proper; windings rI4 and I0 adding inVY the line, equally dividing the line loadbetween ,75e e,

|73, 32 and a3 being Y ,Y i f 3oY n vIr'tei'erring to theifunctions and balance 'of the 'f Vparallel line'circuit 2,'th'e operation isbest illus-` i Y 45 n ing I4 traverses Vthe ,parallel'circuitf Via i5 to;Y Y

CTI

PII

secondary windings I4 and IB, and between primary windings I3 and Q of the load-balancing circuit 4; balancing impedance being controlled at 49 regardless of said load. It is seen that if line I is opened, winding Ill becomes ineffective, in which case there would be combined E. M. F. from windings I5 and I4, through winding II from point I8, being opposed only by the E. M. F. of winding II; therefore the dividing impedance is provided at I6 to adjust for voltage drop through line I in practice to establish the balance of circuit 2; the same voltage proportion being maintained, but at any required value determined by the lines connected to the repeater.

Input voice currents from Zine Input currents from line I through Il), II, I4 and I5, function differently than do the output currents. In observing the other half of the repeater, input E. M. F. from line IA enters the repeater at point IlA, dividing non-inductively through windings IIIA and I5A to point IBA, traversing windings I IA and IilA in series to the line IA again at point ISA; equalizing impedance IIiA being parallel to winding IIA, thus neutralizing primary windings I4A and ISA; such input E. M. F. through series primary windings IIIA and I IA causing secondary input E. M. F. in one side A of the independent load-balancing circuit 4A, through winding 9A, thence through the input transformer 22A to the other line I, traversing the amplifier.

3l of the independent circuit 4, connecting at i9 and 59 may connect at 5I and 52 instead., for lower potential for use at 3l.

54 and 54A are audio transformers connecting tubes 23 and 43A, and 23A and 43. 22 and 22A are audio input transformers connecting the independent load-balancing circuits 4 and 4A with the rst audio tubes 23 and 23A from lines I and IA respectively.

55 is the power-pack transformer arrangement; the rectifying tube and associated winding not being shown. X and Y indicate the filament connections between said power pack 55 and audio tubes 23 and 23A, and 43 and 43A; the point of B voltage distribution being shown as 69.

Associated circuits Low-frequency signal and noise-blocking condensers are shown in line I and in line IA at points 4S and 48A.

Assuming that the line currents come in on line IA and are repeated out to line I, it will be understood that in grouping elements of the invention that the numerals Il, 32, 9, I3, 33, 3l, 38, 4B, lil, 42, and 3%, indicate an independent loadbalancing circuit; that numerals 20A, 32A, 9A, 39A, 3A, 3A, and 48A, indicate an input section of said load-balancing circuit; that numerals 24, 25, 8, I2, 26, 2l, 28 and 29, indicate an unbalancecornpensating circuit; that 55, 3I, 3G and 43, indicate a source of amplified output power; that numerals 2, IB, II, I4, I5, I6, 45, 45, 47, I'I, 34 and I3, indicate a parallel output load-dividing circuit; that numerals IIIA, I5A, 45A, 46A, 47A, and IISA, indicate an input E. M. F. neutralizing circuit; that numerals 24, 25, 8, I2, 2'I, 28, 26, 29, I3 and 2l indicate an input volume control and counter-E. M. F. balancing circuit; that numeral 55 indicates a source of repeater power E. M. F. circuit; that numeral 44 indicates a gain-control circuit; that numerals 22A, 23A, 54A, 44, 43, 3D, SI, Ell and 55, indicate an amplifying circuit; that the numeral 48A indicates a line low-frequency signal and noise blocking device; that IA indicates a line terminal, and that the numeral 22A indicates a primary source of amplifier input. Assuming that the line currents come in on line I and are repeated out to line IA, it will be understood that the numerals 4A, 32A, SA, 33A, SIA, 38A, 45A, IIIA, 42A, and 39A, indicate an independent load-balancing circuit; that numerals 2li, 32, 9, 39, 3, 3 and 4D, indicate an input section of said independent load-balancing circuit; that numerals 24A, 25A, 8A, IZA, EEA, 23A, 28A, and 29A, indicate an unbalance-compensating circuit; that numerals 55, BIA, 30A, and 43A, indicate a source of amplified output power; that 2A, ISA, IIA, IIIA, I5A, IIiA, 45A, 4t`A, fllA, IIA, 34A, and IBA, indicate a parallel output loaddividing circuit; that Il, I5, 45, 4t, 4l, and I8 indicate an input E. M. F. neutralizing circuit; that numerals 24A, 25A, 3A, IZA, ISA, ZIA, 253A, 21A, 26A, and 29A, indicate an input volumeccntrol and counter-E. balancing circuit; that numeral indicates a source of repeater power E. M. F. circuit; that 44A indicates a gaincontroli circuit; that 22, 23, 54, 44A, 43A, 38A, 3IA, 6G and 55, indicate an amplifying circuit; that numeral 48 indicates a line low-frequency signal and noise blocking device; that I indicates a line terminal, and that the numeral 22 indicates a primary source of amplifier input.

Assuming that the line currents come in on line I, and are repeated out to line IA, the more essential elements of the invention are the input E. M. F.neutralizing circuit designated by numerals I4, I5, 45, II and I5; the independent load-balancing circuit 4A, 32A, 9A, ISA, 33A, 37A,

38A, 39A, 49A, 4IA, and 42A; the parallel output load-dividing circuit 2A, ICA, IIA, I4A, I5A, IEA, 45A, 45A, 4'IA, I'IA, 34A, and ISA; the input volume-control and counter-E. M. F. balancing circuit 25, 2S, 8, I2, I3, 2| and 24, and the unbalance compensating circuit 24A. Assuming that the line currents come in on line IA and are repeated out to line I, the more essential elements of the invention are the input E. M. F.- neutralizing circuit designated by the numerals IIIA, ISA, 45A, IIA, and ISA; the independent load-balancing circuit Il, 32, S, I3, 33, 3l, 38, 39, 4G, 4I and 42; the parallel output load-dividing circuit 2, IU, II, I4, I5, I5, 45, 43, 4l, Il, I8, and 34; the input volume-control and counter- E. M. F. balancing circuit 25A, 28A, 3A, IZA, I3A, ZIA, and 24A, and the unbalance-compensating circuit 24.

Elements such as may be omitted or included as the circumstances and conditions may require, are the Vernier balancine circuit indicated by the numerals 3l, 33, 49, and 5i); the inductance 4Q; condenser 4I; taps 46, 4l, 5I and 52, and repeating coil 26.

While the description and drawings illustrate vin a general way certain elements and arrangements thereof, which may be employed in carrying the invention into effect, it is obvious that many modications may be made in the various details without departing from the scope of the appended claims, it being understood that the invention is not restricted to the particular eX- ample shown and described.

The invention claimed is:

l. A two-way amplifying self-balancing telephone repeater having at either end a transformer arrangement embodying a balancing bridge circuit of two arms composed of transformer windings in which output currents are equalized, and having a winding of said arrangement terminating and connecting between said windings of said two arms, said winding and4 one of said arms being ran input circuit, said windinghaving differential relation to such equalized output currents; an unbalance compensating circuit having windings i differentially associatedY Y condenser interposed between said line terminal and said one of said two arms and blocking low frequency noise and signal currents, and passing voice frequencies. Y l n 2. A two-way .amplifying telephone repeater which when considered from either end of same comprises an independent load balancing circuit' having two balancing transformers, an amplifier output transformer and a bridged inputfcircuit transformer and having two identical'sections of two windings each, one of which serves asV an input section, including said bridged input transformer; an unbalance compensating circuit hav-V ing one winding each in respective Ybalancing transformers in both of said two sections and which functions without a condenser means and having resistance `means and repeating coil means series connected in said unbalance compensating circuit and serving principally as an input volume control and counter line E. .M. F.

y balancing means and serving partially as an un-V balance compensatingmeans, having 'diiferential secondary relation to output currents in said load balancing circuit through said transformers; a counter line E.` M. F. balancing circuit which functions the same as the input volumecontrolmeans, thus partially balancing input counter line E. M. F. in both sections of said load balancing circuit, thereby partially neutralizing counterl output currents which appear asV input currents and which are due to irregularities of line impedance; and an amplifying circuit serving to amplify'voice currents from one telephone circuit to any telephone circuit Yassociated with the rlrst mentioned telephone circuit, through said` telephone repeater.

3. A two-way amplifying Ytelephone repeater which when considered from either end of same comprises two amplifiers, and two sets of'balancing transformers interconnected with said amplifiers; aline terminal Vto which the usual telephone circuitis connected; .a line low-frequency t signal and noise blocking condenser which passes high frequency voice currents and blocks out low frequency currents,` said blocking condenser being interposed between said line terminal and repeater proper; a bridged input transformer;

an input transformer having two joined loaddividing circuit windings, one load-balancing circuit winding and vone unbalance compensating circuit winding; an input E. M. F. Vneutralizing transformer having two joined load-dividing circuit windings,.one load balancing circuit winding, and one unbalance compensatingV circuit winding; an output transformer having two pri.- mary windings and two secondary load-balancing circuit windings; aV high resistance element;

Va series parallel line output load dividingV circuit including said two load-dividing circuit windings of said input transformer, and including said two load-dividing circuit windings of primary windings of said load balancing circuit,

said input E; M. F. neutralizingtransformer, the latter said two windings being parallel connected in said parallel `circuit and having vnon-inductive'relation toinput currents, one of said two load-dividing circuit' windings of said input transformer, being differentially connectedA to one of saidrtwo load-dividing circuit windings of said input E. M. F.,neutralizing transformer, said latter two windings having differential relation to output currents and one of said two load- '13 dividing circuit input windings being seriesr connected to said parallel circuit in series relation to the other of said two load-dividing circuit input F. neutralizing windings, Vsaid latter two windings having inductive relation to outl:

put currents, said series connected windings being series connected in said telephone circuit and being the secondary output windings in said input transformer and said input E. M. F. neutralizing transformer said two differentially con- .nected windings being neutralized by output E. M. F., one side of thevtelephone circuit con-V necting to the junction between'saidtwo loaddividing circuit E. M. F. neutralizing windings;

an adjustable line impedance series connected between said two series connected secondary output windings; a'high resistance element se-Y ries connected between said differentially connected windings yan independent load balancing circuithaving two sections of two windings each'. which performs Ythe function ofY balancing said connected bridged input transformer in relation to output currents and neutralizing same to out-` 'Y put currents, the primary winding of said bridged f input transformer being combined with said load. balancing circuit andu connectingfat the junction said two load dividing circuit secondary loutput windings respectively ofsaid input transformerV and said input E. M. F. neutralizing transformer, said later two primary windings having series relation withthe other two of said two windings per section; a center tapped inductance series connected between said other two windings ofsaid two windings per section; an amplifying circuit serving to amplify and to repeat voice curk rents from one telephone circuit toY another from said load balancing circuit through said bridged input transformer and through said output transformer toisaid load balancingrcircuit,` the secondary windings of'said output transformer being the other two of said twoV windings per section Yand having series relation to said two said two secondarywindings beingY series connected through said center tappedinductance,l said-bridged input transformer primary windingV being connected to said center tap; an unbalance compensatingY circuit, having adjustable imped ance series connected with said unbalance compensating circuit lwinding Yin-said input transformer and with said unbalance compensating circuit winding in said input E. M. F; neutralizing transformer, the unbalance compensating circuit thus having secondary relation in saidY input transformer and primary relation in saidV input E. M. F. neutralizing transformer and thus Y between said two Vload balancingfcircuit windings Y in respective sections having primary relation to serving to modify characteristic of input cur,

rents, to said bridged inputtransformer through 7 said unbalance compensating circuit and to maintain equalization of output currents in'said two sections of said Vload balancing circuit, said unbalance compensating windings beingdifferentially connected in relation to kbalanced out- V7 put currents through said sections of said loadbalancing circuit, output currents flowing through the unbalance compensating circuit when the impedance of one of saidsections of said load-balancing circuit is less or more than the impedance in the other of said two sections, the output current thus owing through said unbalance compensating circuit from one of said sections inducing counter-balancing E. M. F. in the other of said two sections of said load-balancing circuit, the phase and value of such E. M. F. being determined by said adjustable impedance.

4. A repeater for amplification of currents of voice frequency which receives and transmits same at both ends concurrently, said repeater when considered from either end of same embodying an assemblage of transformers comprising an independent output load balancing circuit cornposed of two sections, having two windings each, one of which sectionsV is an input section including a bridged input circuit common to both of said sections, said input section having a winding through which the telephone line current enters; a parallel line circuit having an input transformer through which it has primary relation to said input section and having an input E. M. F. neutralizing transformer, in which neutralizing transformer input E. M. F. from the said telephone line is neutralized in the other of said two sections of said load balancing circuit, such E. M. F. entering said input section of said load balancing circuit by way of said winding of said input transformer in said input section of said independent load balancing circuit; a parallel line output load dividing circuit having an input transformer and an input neutralizing transformer and including an adjustable line impedance, which serves to equalize said parallel load dividing circuit and thus serves to neutralize input E. M. F. in said 'neutralizing transformer at one of said two sections and to equally divide output load in both of said input and input neutralizing transformers in Said two sections of said load balancing circuit; an input volume control and padding circuit common to both said sections through mutually associated windings in said transformers by which said padding circuit serves to partially balance input current in said load balancing circuit and to partially neutralize said bridged input circuit to input current, said padding circuit being anunbalance compensating circuit common to both said sections through said windings in said input and input neutralizing transformers, and serving also to maintain the balance of the output current in said two sections of said load balancing circuit regardless of impedance fluctuations in the telephone line, reflected in the parallel line load dividing circuit; and an adjustable line impedance said impedance being a load dividing element and an input neutralizing element in said parallel line load dividing circuit.

5. A two-way telephone repeater, which when considered from either end of same comprises a parallel line circuit composed of an input transformer and an input E. M. F. neutralizing transformer; an independent load balancing circuit having two opposite sections of two series windings each, one of which sections includes a secondary winding of said input transformer, said one section serving as an input circuit and including one of two primary windings of a bridged input circuit transformer, said winding being common to both said sections; an inductance means series connected in said load balancing circuit and having a center-tap connection forming one terminal of said bridged vinput circuit transformer primary winding; a Vernier balancing resistance having a variable center tap forming one terminal of the second one of said two primary windings of said bridged input circuit transformer and having series parallel relation to said independent load balancing circuit, said vernier balancing resistance and second primary winding functioning as a close balancing means with reference to said bridged input circuit transformer having two primary windings, the counterbalancing output E. M. F. of one of said two windings being controlled by said Vernier resistance; a parallel line output load dividing circuit including series dividing resistance and having secondary relation to said load balancing circuit through windings of said input transformer in one of said two sections and through windings of said input E. M. F. neutralizing transformer in the other of said two sections, the line impedance reflected in the line windings of said load dividing circuit being thus equalized in associated windings of said transformers in said two opposite sections of said load balancing circuit, thus balancing said bridged input circuit transformer in relation to output E. M. F. through said two sections; an input volume control circuit having a series resistance means, said volume control circuit being common to both said two sections and having secondary relation in said input transformer and primary relation in said input E. M. F. neutralizing transformer which thus functions to partially balance said bridged input circuit transformer to input current by partially equalizing input currents in said opposite sections of said load balancing circuit by said series resistance means, such input currents being in the same direction in both said sections, said load balancing circuit, said input volume control circuit and said load dividing circuit all being inductively connected through respective windings in said input transformer and in said input E. M. F. neutralizing transformer, in said two opposite sections.

6. A two-way telephone repeater, which when considered from either end of same embodies an assemblage of interconnected transformers, an amplifier output transformer, an input transformer, an input E. M. F. neutralizing transformer and a bridged input circuit transformer, and comprises an independent load balancing circuit having a center tapped inductance means of load balancing circuit resistance control, and including said bridged input circuit transformer and comprising two opposite sections of two windings each, including secondary windings of said amplifier output transformer, one of which two identical sections being an input section having a secondary winding of said input transformer and including one primary winding of said bridged input circuit transformer, the other of which two sections having a secondary winding of said input E. M. F. neutralizing transformer and in both of which sections output currents are equalized, said input and said input E. M. F. neutralizing transformers serving also as output transformers; a parallel line output load dividing circuit comprising two non-inductively connected primary windings of said input E. M. F. neutralizing transformer and two series connected primary windings of said input transformer, said parallel line output load dividing circuit including an adjustable line impedance between said transformers, said load dividing circuit serving to neu lize input currentin one section of said load balancing circuit and to equally dividerout- -put impedance both sections of said load balancingcircuit through said input and saidinput E. M. F. neutrai ing transformers; an input volurne control circuit having avariable resistance /andhaving a secondary winding in said input transformer and a primary winding insaid inputli. M. F. neutralizing transformer and which functions to'partially equalize input currents in both sections of said load balancing circuit, input currents thus passing from the; input section to Vthe other of said two sections throughY said input volume ycontrol circuitl thus partially Vreducing input volume; by'partially balancing said bridged input circuit transformer to saidrinputV currents in the same direction both said sections.

` '7. A `two-way telephone repeater which when considered. from eitherzend of same comprises an .independent load balancing circuit of two sec- .tion'sone of which is an input section, each section yhaving Yaprimary output winding which is also a secondary .input winding, said windings having a bridging condenser means, said condenser means serving as an output control shunt Y line impedance in said primary windings of said v,load balancing circuit through said secondary Y-windings of'said load dividing circuit; said secondary windings being seriesj connected in the line on' opposite sides of said dividing impedance;

an input E. M. F. neutralizing transformer hav-V ing two non-inductively connected primary lineV Ywindings which neutralize input E. M. F in said secondary input winding in one section of saidY load balancing circuit; kan input transformer having two series parallel` connected. primary line windings which inductivelyincluce'input E. M. F. Vin said Ysecondary winding in the other section of said load balancing circuit servingV as the input section; and an inputvolume control circuit having variable impedance elements and having series windingssecondary to both said sections and serving to control the volume of input F. in'said inputsection'of said load balancing cirouitfby introducing input F. in the other of said two' sections from said input section throi-gh said input volume control circuit. f

' A 8. duplex telephone repeater which when cnnsideifed from either end of same consiststof Vtwo amplifiers; an input and an output arrangement Y of transformers associated with saidtwoV ampliers'in such manner that the amplifier in one direction does not interfere withithe amplifier in the other-direction; a parallel outputfload dividing circuit; a source of amplified output power, consisting of a conventional arrangement of amplifying valves Yand transformers; an inde- V' pendent load balancing circuit having two seci 'Y Vtions of two windings each aand-having Variable 'balancingV resistance commento both sections, and being interposed between said amplified out-l putA power source and said parallel output loadY dividing 'circuit, the repeater balancing impedance being thus controlled independently of line impedance; a parallel iine output load dividing circuit, serving to partially balance inputcurrents adam 1a cuit having an input E. yM. F. neutralizing transformer, an input transformer, and anadjustablcv output load dividing impedance 'interposed and series connected between secondary output windings of said transformers, and serving to `admit input current to onev section ofisaid load balancing circuit and to exclude inputA current from the other section, said input Vtransformer having inductive relation to one. section and Vsaid input E. M. F. neutralizing transformer having noninductive relation tof'theother of said sections, and serving to equalize output current in rcspective primary win-dings of said two sections of VVsaid load balancingjcircuit associated with said' two series connectedsecondary output windings,Y both said transformers having inductive relation to respectivelones of said sections, one side of said Y parallel lineoutput load-dividing circuit including a tappeti inductance means comprising one secondary winding each of said transformers, and which as an impedance element, serves as a semiselfbalancing means, confining variationsV Ofiline impedance to the other respective secondary windings of said transformers comprising Y'said load dividing means, which thus functions to Yminimize repeater unbalance due to changes injline of saidY parallel output load dividing circuit to be used at will, in lieu of said inductance means and impedance; a high resistance means in saidside unbalance compensating circuit in connection with said load balancing circuit,'and having inductive relation to said two'sections through associated primary and secondary windings of said two transformers.

' 9. A two-way telephone Yrepeater which when considered from either end of same consists of an interconnected set cf transformers comprising a bridged Vinput circuit transformer primary winding; an independent load balancing circuit of Vtwo identical sections of two windings each, in-

cluding an amplifier secondary output winding and a load Vbalancing circuitY primary Youtput winding, said sections having parallel bridging connectiori to said input circuit transformer primary Vwinding, said section windings being series connected; a parallel line output load 'riding circuit naving 'an 'adjustablef line` dii'iding impedance,V an input Vtransformerhaving two secondary windings, and an input F. nentralizing ,transformer having two secondary windings; a high resistance means combined withV one side of said parallel circuit restricting re- Y ections of line impedance to the Vother, side including dividing impedance; an unbalance'icompepsating circuit including series variable impedance units whichY functions to neutralize excess output E. M. F. either section of said load Vbalancii'ig circuit at low impedance with output E.Y from the other secciv.

connected tion of said load balancing circuit at highjV in both sections of said load balancing circuit,

thus partially balancing said bridged input circuit transformer primary winding.

10. Av two-way amplifying telephone repeater which when considered from either end of same comprises an independent load balancing circuit having an associated unbalance compensating circuit, a multiple connected Vernier balancing circuit, a shunt condenser impedance control means, a series connected center tapped inductance multiple connected with said condenser means, an input section and another section; an amplifying circuit which amplii'ies voice currents, said amplifying circuit comprising a source of amplified output power, and a parallel line output load dividing circuit having .two balancing transformers between which circuits said load balancing circuit is interposed; a source of repeater power E. M. F. circuit which actuates said amplifying circuit in its voice current amplifying function; a calibrated gain control circuit which determines the degree of amplification of said voice currents through said amplifying circuit; a parallel input E. M. F. neutralizing circuit and a series parallel input circuit which are component parts of said parallel load dividing circuit functioning to inductively neutralize input currents in one of said two transformers at one section of said load balancing circuit, and functioning to admit input current through the other cf said two transformers into the other one of said sections; a primary source of line input comprising the usual associated telephone circuit; a line terminal at which said telephone circuit is connected to the repeater, and a line low frequency signal and noice blocking device effecting high resistance to low frequencies and low resistance to high frequencies, said device being series connected at said line terminal.

11. A two-way amplifying telephone repeater which when considered from either end of same embodies an assemblage of balancing transformers comprising an independent load balancing circuit of two opposite sections one of which is an input section, having an amplifier output transformer and two balancing transformers, each of said two opposite sections including one winding of said output transformer and one winding respectively of said two balancing transformers, said windings of said output transformer being series connected to both said windings of said two balancing transformers, respectively; a shunt condenser means for circuit impedance control and another shunt condenser means for output volume control and characteristic modiiication, multiple connected to both said windings of said two balancing transformers; a Vernier balancing element, multiple connected to both said windings of said balancing transformers and said shunt condenser in said independent load balancing circuit; an inductance means, which, being in multiple connection with iirst one of said condenser means, determines load balancing circuit impedance, independently of telephone line impedance, said inductance means being center tapped and series connected between both said windings of said output transformer, the center-tapped point of said inductance means intersecting both said sections; an unbalance compensating circuit having variable impedance and having secondary relation to both said sections through respective windings of said two balancing transformers which compensating circuit automatically maintains equalization of output currents in both said two sections regardless of reflected fluctuations of line impedance in one of said sections thus maintaining repeater balance, a parallel line output load dividing circuit having an adjustable line dividing impedance and having secondary relation to both sections of said load balancing circuit through said balancing transformers causing said two balancing transformers to function also as an input E. M. F. neutralizing transformer and an input transformer respectively, said parallel load dividing circuit admitting input currents to one of said two sections and excluding input currents from the other of said two sections of said load balancing circuit, and to equalize output line irnpcdance in said opposite sections of said load balancing circuit; a source of amplified output power comprising a two stage amplifying circuit having two tubes and two transformers, and having primary relation to said load balancing circuit through said output transformer; a calibrated gain control circuit, associated with said amplifying circuit, and serving to control ampliiication; and a line terminal at which the usual telephone circuit is connected to the repeater.

12. A two-way amplifying telephone repeater which when considered from either end of same includes a telephone line circuit; an independent load balancing circuit having an input section and another section, said input section including a bridged amplifier input transformer, and having a center tapped inductance means serving to determine the operating resistance of said load balancing circuit; an amplifying circuit comprising two matching transformers with two associated amplifying tubes and including a calibrated gain control, said amplifying circuit being interposed between said input section and said load balancing circuit at opposite ends of said telephone repeater; an unbalance compensating circuit having adjustable impedance, said compensating circuit having secondary relation with said sections and functioning with said load balancing circuit as a filter circuit to determine the voltage frequency characteristic of input currents to said input section of said load balancing circuit, thus characterizing input currents to said amplifying circuit; two balancing transformers; a parallel output load dividing circuit including two joined windings each of said two balancing transformers and having an adjustable line impedance means series connected in one side of said parallel output load-dividing circuit, said parallel circuit thus comprising four windings, one side of said telephone line circuit connecting to one of said transformers at the junction between two of said joined windings, said two windings having parallel and non-inductive relation to input currents from said telephone line circuit, thus being neutralized by input current, said adjustable line impedance means connecting at the junction between two of said joined windings of the other of said transformers, the line circuit thus passing through one winding of one transformer at one section, through said dividing impedance, through one winding of the other of said transformers at the other said section to the other side of said telephone line, the other two windings of said transformers respectively being connected together to form a circuit parallel thereto, and having differential relation to output currents; and a line low frequency signal and noise blocking device series connected in said telephone line circuit and serving to exclude low frequency currents from, and to admit high frequency currents to the telephone repeater.

loY

k13. A two-'way amplifying telephonerepeater vconsisting of` transformer connected circuits which when considered from either end of same comprises a differentially Aconnected unbalance compensating circuit having a series connected adjustable impedance; an independentl load bal.'-

ancing circuit having two sections including an input section, and having a bridged amplifier input transformer connected common to both s-ections, one of which sections functions as an input section in relation to said unbalance compensatingcircuit in conjunction with said adjustable impedance, said compensating circuit having low resistance, the other of which sections functions as the input section in relation to said unbalance Ycompensating circuit having comparatively high resistance, said unbalance compensating circuit Vhaving series connected windings associated with both said sections; a parallel line output load dividing circuit having inductiverelation to said Y load balancing circuit and comprising an input section having an input transformer and an input neutralizing section having an input E. M. F. neutralizing transformer, and serving to admit input currents of low potential to one section only of Vsaid load balancing circuit through said input transformer and to admit input currents to one winding only of said unbalance compensating circuit, in said input transformer; providing a low resistance input filter circuit through which circuit input currents Yof high potential from said input transformer pass to said input section of said load balancing circuit, an amplifying circuit,

V'the characteristic of whose amplified currents is determined by the characteristic of said unbalance compensatingcircuit; a source of repeater Vpower E. M. F. circuit which is connected to and actuates said amplifying circuit; a'source of line input connected to and from which input currents enter said parallel load dividing circuit; and aline Yterminal at which the telephone circuit Vcomprising said source of line input, is connected Y tothe repeater.

Y 14. A two-way amplifying and self balancing telephone repeater which when considered from either end of same comprises a primary source ofV line input, which, in either direction, comprises the usual associated telephone circuit; a line terminal at which the telephone circuit is connected to the repeater; a line low frequency signal and noise blocking device interposed between said terminal and the repeater; an input E. M. F. neutralizing transformer;` an input` transformer having a winding joined to a winding of said neutralizingl transformer; an output transformer;

a center tapped inductance and a bridged input circuit transformer connected to said center tap and to the junction between said two joined windings; an independent load balancing circuit having two sections one of which serves as an input section, and simulating a bridge'shaving two arms, on-e arm including a winding of saidinput transformer,y the other arm including` a winding of said input neutralizing transformer, each armY including a winding of said output transformer,

both arms being connected together between said two joined windings and through said center tapped inductance; an unbalance compensating circuit serving as an automatic balancing circuit andas an input volumercontrolv and characterizing circuit inductively'connected to said load balancing circuit through diierentiallyconnected windings at both said sections in said input and input neutralizing transformers, and serving to automatically balance output currents in said two sections; an amplifying vcircuit inductively connected to said load balancing circuit through said output transformer and transmitting amplified alternating currents to same;- a parallel output Y load dividing circuit having inductive connection to'said load balancing and said unbalance cornpensating circuits throughsaid input and input neutralizing transformers, causing `input currents from one telephone circuit which traverse said lin-e terminal and said low frequency blocking device toV traverse saidV input neutralizing transformer of said load dividing circuit, said input transformer of vsaid load balancing circuit, said unbalance compensating circuit, causing said unbalance compensating circuit to function as an input volume control Vand characterizing circuit, said Yinput section, said bridged input circuit transformer, said amplifying circuit, said load balancing circuit inductively connected to saidYV unbalance compensating circuit, Vcausing said unbalance compensating circuit to function as an unbalance compensating circuit, vsaid parallel line output load-dividing circuit, said line low frequency signal andrnoise blocking device, said line terminal to the other associated telephone circuit. y

15. A two-way self balanced telephone repeat- Ver which when considered from either-end of same comprises a primary source of line input consisting of conventional telephone circuits; line low frequency signal and noise blocking ycondensers' series connected in said telephone circuits and with said source, and serving to block out low frec quency currents from said source; an output transformer; an input E. M. F. neutralizingtransformer having two parallel connected line wind'-V ings series connected with Vsaid source and inductively neutralizing inputV currents from said source, in said parallelY connected windings; an input transformer having two series parallel connected line windings in which input currents are inductive; an amplier input transformer; an input circuit having a winding in said amplifier input transformer series connected with a winding in said input E. M. F. neutralizing transformer through which circuit 'input currents are thus admitted to said amplifierv input transformer; an

unbalance compensating circuit having variable Y impedance elements series connected and serving as an input characterizing circuit, said unbalan'ce compensating' circuit having windings in said input and inputE. M. F. neutralizing transform-` ers and through which input currents pass from said input transformer toV said input circuit in said input E. M. F. neutralizing transformer; an

former and having two sections of two windings each in which amplified output currents are equalized, said amplifier input transformer intersecting and beingbridged across said two sec- Y tions; an unbalance compensating circuit having variable impedance elements series connected and V Y having inductive connection to said two sections through respective windings in said input and input E. M. F. neutralizing transformers and automatically maintaining balance of output currents in said two sections; a parallel line output load dividing circuit having inductive relation to said two sections through windings in said input transformer and in said input E. M. F. neutralizing transformer which equalizes output line impedance in said two sections of said load balancing circuit through mutually associated windings in said transformers; and aline terminal through which telephone repeater input currents from said primary source of input, traverse said line low frequency signal and noise blocking condenser, said input E. M. F. neutralizing transformer, said input transformer, said unbalance compensating and characterizing circuit, said input section of said load balancing circuit, said amplifying circuit, said independent load balancing circuit, said parallel load dividing circuit, said line low frequency signal and noise blocking condenser, and said line terminal.

16. A bi-path amplifying telephone repeater which when considered from either end of same comprises the following elements in its function of repeating and amplifying alternating currents from a primary circuit to a secondary circuit in both directions concurrently, and in preventing said amplified currents from returning to the respective primary circuit; a line terminal connected with each of said circuits; a line low frequency signal and noise blocking condenser series connected in each of said circuits and serving to block out low frequency signal and noise currents from said associated circuits; a parallel line input E. M. F. neutralizing transformer connected to each of said circuits and inductively neutralized by input currents from said circuits; an input transformer series parallel connected to each of said input E. M. F. neutralizing transformers through which input currents are inductively admitted to the repeater; a variable divided impedance; a parallel-line output load-dividing circuit embodying said input E. M. F. neutralizing transformer, said input transformer and said variable divider impedance; a bridged amplifier input transformer; an independent load balancing circuit embodying said bridged amplifier input transformer and having two sections, one of which serves as an input section associated with said input transformer of said load-dividing circuit, the other section being associated with said input E. M. F. neutralizing transformer of said load dividing circuit; an unbalance compensating circuit having inductive connection with said two sections through said input and input E. M. F. neutralizing transformers and serving principally as an input volume control and a counter E. M. F. balancing circuit, for conditions not requiring imbalance compensating, and having series connected resistance control; an output transformer; an amplifying circuit inductively connected to said load balancing circuit through said output transformer and serving to amplify and repeat voice currents from said input section through said bridged input transformer of said load balancing circuit; and a calibrated gain control connected in said amplifying circuit determining degree of amplification in decibels, said calibrated element being combined with said amplifying circuit, in a manner to control E. M. F. of amplified currents.

17. A two-way amplifying telephone repeater embodying an assemblage of interconnected transformers and which when considered from either end of same comprises a line terminal to which the telephone circuit is connected; a line divider-impedance; a variable high resistance means; a line low frequency signal and noise blocking condenser through which amplified voice currents are transmitted, from the repeater to said telephone circuit, but which serves to block out amplified currents of signal and noise frequency; an input transformer; an input E. M. F. neutralizing transformer; an output transformer; a parallel line output load dividing circuit having said adjustable line divider-impedance and having two joined windings of said input transformer and two joined windings of said input E. M. F. neutralizing transformer, the four windings being series parallel connected to the line at the junction between said two joined windings of said input M. F. neutralizing transformer, one winding of each of said two windings in said transformers being series connected to the line at the terminal of one of said two windings of said input transformer, with said divider impedance series interposed between said windings, and one Winding each of said two windings in said transformers being series connected with said variable high resistance means, said one winding each and said high resistance forming a circuit parallel to said divider resistance and said one winding in said input E. M. F. neutralizing transformer, and connecting series parallel at the junction between said two joined windings of said input transformer of said output load dividing circuit; a bridged input circuit transformer; an independent load balancing circuit having two sections of one winding each of said input transformer and said input E. M. F. neutralizing transformer and having a winding of said bridged input circuit transformer connected to and intersecting both said sections, one of said sections serving as an input section, amplified output currents being transmitted to said windings of said parallel-line output loaddividing circuit through said windings of said two transformers in said two sections; a source of ampliiied output power having two inequality matching transformers and said output transformer, comprising an amplifying circuit, having an output tube and an input tube, and which transmits amplified voice currents to said load balancing circuit, the two amplifying tubes of said amplifying circuit being connected by one of said inequality transformers, the output tube being connected to said load balancing circuit through said output transformer having a winding in each of said two sections, said input tube being connected to said input section through a secondary winding of said bridged input circuit transformer, bridged across said load balancing circuit; two variable impedance elements; an unbalance compensating circuit having a winding in said input transformer and a winding in said input E. M. F. neutralizing transformer series connected with said two variable impedance elements through which input currents are modified in characteristic, in passing from said input transformer to said input section of said load balancing circuit.

18. A two-way amplifying self-balancing telephone repeater consisting of two arrangements of bridged input circuit inequality transformers, output transformers and balancing transformers interconnected with two amplifiers, which when considered from either end of same comprises an independent load balancing circuit having two sections of two windings each, one of which serves as an input section which includes such bridged input circuit inequality transformer'connected to and common to both such sections, such transformer comprising'a high impedance secondary winding and a center tapped two winding'prirnary of Vlow impedancabne winding serving as the bridged input element; a'high resistance poten- 'rticrmeter having a variablecehter tap; a Vernier balancing circuit series parallel connected Yte such load' balancingV circuit and including two windings ofgsuch output transformer and including said series high resistance potentiometer having a vari-V able center tap andrincludingone winding ofV such kcenter tapped primary of such inputcircuit inequality transformer, said one winding of such center tapped primary being differentially reiated to the otherprimary winding and serving to closely balance said bridged input circuit transformerv Y in relation to output currents through said two sections, thus neutralizing said input circuit transformer to output currents, said verni` circuit winding being connected to said Vernier circuit through saidl potentiometer center tap; a

series.parallel-line output load-dividing circuit having series connected variable dividing-impedance and having two windings of one of such balancing transformers inductively connected to one of saidl two sections through one of said two windings per section, and havingA two windings of the otherof said balancing transformers inductively connectedto said input section through one of said Ytwo windings perrsection, which load dividing circuit functions to equalize output load in Vsaid,

ltwosecrtiens of saidV independent load balancing circuit, through such balancing transformers, one

winding each of :said two windings per,V transformer being series connected with the telephone circuit, said dividing-impedance being interposed between Vsaid series connected windings, one winding each of said two windings being VdifferentiallyV connected and forming a parallel circuit, said par allel circuits beingseries connected to one of said Y two windings in one of saidrbalancing transu formers at said input section, said series parallel circuit having series parallel connection to the telephone circuit; an amplifying'Y circuit having two amplifying tubes and being inductively connected to said load balancing circuit through one for said amplifying tubes, one A. C. winding sup# plying the filament of said rectifying tube, one power winding delivering said D. C. voltage through said rectifying tubeAto said lter, said# filament and'power windings being inductively connected to said conventional A.'C. power supply line through said primary winding, said power E'. M. F. circuit also includingseries cnnected grid-bias resistancesin plate circuits of said amplifying tubes.

19. A two-way'amplifyingteiephne repeater which when considered fromeither end of same 'comprises a bridged, input circuit transformer; a

variable center tapped inductance; Yan independent load balancing circuit having twov sections connected to said bridged input transformer and including said Variable center tappedinductanca.

by means of which circuit said bridged'input cir-Y cuit transformer is balanced independently Vof 'tine impedance; Van input'transformer; an input M. llzneutralizing transformer; a parallel line output load dividing circuit dispensing. with an artificial n balancing line, including said input' E. M. Rgneutralizing transformer and including said inputtransformer and beingeinductivel-y connected to said twol sections threugh said transformers, and serving to equally'divide output load Y i Y in primary windings in'said balancing circuit Vsections; an adjustable Vline-impedance in one side of said'V parallelV line output load dividing circuit which serves as a series line-impedance'divider, and thus equalizing linejmpedance in secondary windings` Vof said transformers respectively, inf said two sections, saidfwindings'having series connection in` opposite sidesof the telephone line- Y at saidtwo-sections; a line terminal to which. a.

, telephonefrcircuit is connected; a line rlow fre-fz' l? quency signal and noise blocking condenser tri-- terposed between said line Vterminal and said par` allel load-dividingcircuit,r said blocking devi-ce passingghigh frequency currents and blocking low frequency currents; an output transformer; an 2 amplifying "circuitiY having inductive connectionr to said'ioadV balancingcircuit through said output` transformer andthrough said bridged input circuit i transformer and serving to amplify andato repeatk voice currents-from onertelephone circuit to another telephoneV circuit; an uri-balance compensating'circuit inductively connected topsaiditwo sections of said load-balancing circuit through re-v spective windings of Ysaid input transformer andv said' input E; M. F; neutralizingetransformer, said unbalance'f compensating circuit compensating changing line impedance reflected in saidy input transformer i-n one of said two sections, thus maintaining .equalization of output currents in said two sections of said loadbalancingY circuit thus'k ccnnected; a high resistance unbalance minimizingunit connected in one side ofr said parallel'r line output4 load dividing circuit, restrict#V ing'line-impeda-nce reflectionsto the parallel load dividingside'; and a:;vernier balancing circuit parallel-connected toV said load balancing circuit and*V having a differentially connected. primary winding in said 'bridged input transformer and serving as a' close vbalancing means in said load balancing circuit. n

20. A two-way amplifying self-balancingtelephonegrepeater which whenconsidered from-eithe er endof' same comprises a line terminal at which tweem said terminal andthe repeater; a series g paralisi line output load dividing circuit having'an input tra'nsformer'andan input EIV'M. F. neutralicing transformer in separate sections serving to equally divide line load in said separate. sec:- tions, one of saidseparate sections servingY asfan input' sectionginput current being neutralized inductively in the-other of said sections,fthe equal'- ization of output currentsV inffsaid separatersections also balancing and; ni'eutralizing one side of 65;'

said parallel lineV circuit to output currents an unbalance compensatingl circuit having inductive relation to both of said-sections through associated seriesl connectedy windingsin'v said^ transformers and serving as characte'rizingv entrance circuit for 70 input currents from saidfinput section of saidl'oadv dividing circuit; andserving also to equalize outfput currents in said separate sections of saidloacl.` dividing circuit; a center tapped'inductance; an

independent load balancing circuit 75 tional impedance and having two sections, one section including a winding of said input E. M. F. neutralizing transformer and serving as an input section, the other section including a winding of said input transformer, said sections having connected a bridged input circuit transformer, said independent circuit comprising an intermediate balancing circuit, not an artificial line, for the purpose of repeater balance, independently of line impedance, by means of said center tapped inductance, and having inductively associated said unbalance compensating circuit by means of which output currents in said load balancing circuit are automatically equalized in said sections and in said separate sections of said parallel line output load dividing circuit.

21. A two-way amplifying telephone repeater which in amplifying and repeating voice currents from one repeater associated telephone circuit to another repeater associated telephone circuit, prevents the return of amplified currents to the input telephone circuit, without artificial-line circuit balancing means, said repeater having a plurality of circuits inductively connected with each other, said repeater when considered from either end of same embodying a plurality of interconnected balancing transformers, said balancing transformers including said circuits, said repeater comprising a line terminal interposed between each associated telephone circuit and one of said circuits; a line low frequency signal and noise blocking condenser device serving to block low frequency current and to pass high frequency current, and being interposed between said line terminal and one or said circuits; an amplifying circuit having an input transformer with bridged input circuit windings, and an output transformer; a parallel-line output load-dividing circuit; an independent load balancing circuit of two arms and having secondary relation to said amplifying circuit through said output transformer and including said bridged windings of said input transformer, said load balancing circuit having prlmary relation to said load dividing circuit through certain of said plurality of loadbalancing transformers; an unbalance compensating circuit having secondary relation to said load-balancing circuit through certain of said plurality of load-balancing transformers, said unbalance compensating circuit preventing unbalance of output currents in said load-balancing circuit arms, due to fluctuations of line load in said load dividing circuit; and a source of repeater power E. M. F. circuit associated with said amplifying circuit, and actuating same.

22. A balanced two-way, self-compensating, telephone repeater-which when considered from either end of same includes a balancing bridge of two arms having transformer windings; an input circuit having a winding connected to and centrally intersecting said arms; an adjustable impedance; an amplifier output circuit having windings associated with said arms; a line input circuit composed of transformer windings associated with one of said arms; a line balancing circuit having windings associated with said bridge and equalizing the output impedance of said arms, said line balancing circuit including said adjustable impedance; an amplifying circuit having a winding associated with said input circuit winding connected to said arm; an unbalance compensating circuit having differentially connected windings associated with said windings in said arms.

23. A two-way telephone repeater which when considered at either end of same includes inductively related circuits comprising an automatically counter-balanced input-output balancing bridge of two arms which incorporate an output load-balancing circuit having transformer windings; an amplifier output circuit having inductive relation to said load-balancing circuit through transformer windings associated with said arms; an unbalance compensating circuit having difierential relation to said output load-balancing circuit through said transformer windings of said arms and counter-balancing same; an amplifier input transformer winding having abridged relation to said output load-balancing circuit arms; a line-balancing circuit including an adjustable impedance and having inductive relation to said load-balancing circuit through said transformer windings in said arms and equalizing output impedance of same; a line input circuit having noninductive relation to said load-balancing circuit and said unbalance compensating circuit through said transformer windings in one of said arms, and having inductive relation t0 said load-balancing circuit and said unbalance compensating circuit through said transformer windings in the other of said two arms; and an amplifying circuit associated with said amplifier input transformer winding.

24. A two-way telephone repeater, which in considering either end of same, comprises a bridge of two arms having primary and secondary transformer windings and forming a load-balancing I circuit which includes two arms; an amplifier input winding having bridged relation to said arms; a bridged Vernier balancing input winding having differential relation to said amplifier input winding; an amplifier output circuit having primary windings associated with said arms; a line input circuit having differential windings associated with one of said arms and having inductive windings associated with the other of said arms; a line-balancing circuit including an adjustable impedance and having inductive windings associated with both of said arms and equalizing output impedance of same; an amplifying circuit associated with said bridged amplifier input winding and said Vernier winding.

25. A balanced two-way, self-compensating, telephone repeater which when considered from either end of same includes a balancing bridge circuit of two arms having transformer windings; and including an input circuit having a winding connected to and centrally intersecting said arms; an adjustable impedance; an amplifier output circuit having windings associated with said arms; a line input circuit forming part of said balancing bridge circuit composed of transformer windings associated with one of said arms; a line balancing circuit having windings associated with said bridge circuit and equalizing the output impedance of said arms, said line balancing circuit including said adjustable impedance; an amplifying 1 circuit having a winding associated with said input circuit winding and an unbalance compensating circuit having differentially connected windings associated wth said windings in said arms.

WILLIAM E. HARDING. 

